Rotary conjugate dresser

ABSTRACT

A conjugate wheel dresser for truing a grinding wheel in order to plunge grind surfaces at angles to each other such as the track and rib of the inner race of roller bearings; the mechanism consisting of at least two motor driven dressing cutters, coated with abrasive grits such as diamonds. The dress is accomplished by one pass of the conjugate dresser.

References Cited UNITED STATES PATENTS 9/1966 Seidel...... l25/lll0/l944 Harley.. 125/11 7/1949 Polk l25/l1 2/1969Hoglynd................ 125/11 g a grinding gles to each other of rollerbearings; tor driven dressing ress Primary Examiner-Harold D. WhiteheadAttorney-James H. Bower ABSTRACT: A conjugate wheel dresser for truinwheel in order to plunge grind surfaces at an such as the track and ribof the inner race the mechanism consisting of at least two mo cutters,coated with abrasive grits such as diamonds. The d is accomplished byone pass of the conjugate dresser.

I United States Patent [72] lnventors Walter A. Boyd, Jr.

Woodstock; Leon .1. Barnard; Hugo A. Lakso, both of Springfield, all of,Vt. [Zl] Appl. No. 792,677 [22] Filed Jan. 21, 1969 [45] Patented June1, 1971 [73] Assignee Bryant Chucking Grinder [54] ROTARY CONJUGATEDRESSER 2 Claims, 8 Drawing Figs.

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zf0/V J BAR/YARD H060 A. 1/4/00 A TTORNE V ROTARY CONJUGATII DRESSERBACKGROUND OF THE INVENTION This invention relates to wheel dressing ingeneral, but more especially dressing the grinding wheel for theconjugate form grinding of workpieces such as the conical race and flatrib of roller bearing tapered cones.

The concept of conjugate grinding of two surfaces is not new per se;this method of accomplishing the dress is. In the past it has beencustomary to use one diamond point for each element of the wheelsurface, each with its own piston or motive device, used alternately. Aseach diamond must slowly traverse its surface as the wheel turns,understandably, a considerable time must be consumed during each dresscycle, and, since dressing must be done every I to 20 parts (consideringtheir size), a saving in time is very desirable.

Further, since all'the material dressed from the grinding wheel mustberemoved by one diamond point, the wear is considerable andconsequently the point on the diamond rapidly dulls. Accordingly, onceor twice a day, the diamonds must be rotated. This requires much trialand error grinding to keep withinthe closer tolerances desired, and thetime loss further compounds the problem.

Machine time and man hours being a very significant part ofmanufacturing cost, it is our object to invent a mechanism which willnot only reduce machine down time for replacement or resetting of thedressing tool, but will also speed the actual dressing operation itself.

SUMMARY OF THE INVENTION According to the present invention, thegrinding wheel is dressed by one pass of the conjugate dresser, in whichtwo rotatable abrasive-faced dressing cutters, a track cutter and a ribcutter, dress the grinding wheel. The two cutters are offset relative toeach other so as to dress the grinding wheel in order that the grindingwheel will form grind the track and rib of the workpiece in onesimultaneous grind.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a general environmentalview, partially in section, of the conjugate dresser in place on agrinder;

FIG. 2 is a plan view with a portion of the guard removed.

FIG. 3 is an elevation view looking directly toward the back of thedressing cutter for the rib portion of the grinding wheel;

FIG. 4 is an elevation view looking directly toward the dressing cutterfor the track portion of the grinding wheel;

FIG. 5 is an elevation view looking at the conjugate dresser along aline parallel to the axis of the grinding wheel;

FIG. 6 is a section through the elevating mechanism showing theantifriction slides and piston, including the hydraulic circuit;

FIG. 7 is an enlarged plan view of the cutters in dressing positionshowing the track-forming dressing cutter, the ribforming dressingcutter, and the grinding wheel; and

FIG. 8 is a plan view of the contact between grinding wheel andworkpiece.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, a conventional typeof form grinder is mounted on a bed 10. A wheel slide 12 is mounted forcrossfeed movement as indicated by arrow 13.

The workslide I4 is located on the bed and is mounted for movementlongitudinally as indicated by arrow 15, between the grinding positionas shown and the dressing position as will be explained later on.

Mounted on the workslide 14 is the loader mechanism 16, shown with amagazine 17 containing unground workpieces l9.

Loader arm 18 periodically transfers one workpiece 19a from the magazine17 along arcuate path 20 to work station 21, and deposits it on amagnetic chuck 22, where it is rotated in a typical shoe centerlessmanner by the workhead hidden behind splash guard 23. The loader arm 18is shown raised to better view the work station. Normally the armremains down during the grinding operation.

Directly in front of the work station 21 is the grinding wheel 24partially hidden under the wheel guard 26. The wheel 24 is crossfed intothe workpiece 19a located at the work station 21 until the desiredfinish size is attained. It is then withdrawn as shown by arrow 13.

The finished workpiece I9 is then automatically removed from the workstation 22 and dropped into discharge chute 25 in a manner not part ofthis invention.

Periodically, a dressing operation is required to sharpen the grindingwheel 24. This is performed by the conjugate wheel dresser 28 mounted onthe workslide 14 by attaching baseplate 29 over sub-base 30 which ispart of the workslide. Baseplate 29 is swiveled horizontally about pivot31, and locked in position by tee nuts 32 in slot 33, as seen in FIG. 3and FIG. 4.

Referring to FIGS. 25, we see more detailed views of the conjugate wheeldresser 28 which will now be described more fully. In general, itconsists of two abrasive faced dressing cuttersa track cutter 34 and arib cutter 35each mounted on a motorized spindle. These two cutters aremounted on an elevator block 36, which moves up and down on antifrictionslides 37, separating it from a fixed cylinder block 38. The movementdirection is indicated by arrow 39, as seen in FIG. 4.

The cylinder block 38, which is rigidly bolted to baseplate 29 by bolts27, contains a hydraulic cylinder 41 (FIG. 6) for moving the elevatorblock 36 carrying motorized dressing cutter spindles 61 and 69. A pistonand rod assembly 40 in the cylinder 41 is connected to the elevatorblock 36 through bracket 42, as is best seen in FIG. 6. The hydrauliccircuit will be explained later on.

Looking again at FIG. 1, it will be noted that the internal mechanismparticularly the antifriction bearings 27 is well guarded by housing 51.This is attached to the elevator block 36 by screws 52, allowing it tomove up and down with. the dresser. In order to keep the coolant andgrinding swarf out of the mechanism, an accordionlike bellows 53 isattached between the bottom of the housing 51 and the baseplate 29.

FIG. 7 and FIG. 8 show the plan view of the grinding wheel at thedressing station and at the grinding station respectively. FIG. 7 showsthe relative positions of the track cutter 34, the rib cutter 35, andthe wheel 24. The corresponding position of wheel and workpiece is shownin FIG. 8.

The procedure of setting the dressing cutters will now be described.

In order to achieve the exact profile specified for the workpiece, it isnecessary to very carefully position the track and rib cutters 34 and 35relative to each other, as seen in FIG. 7, so as to dress the grindingwheel to form grind the workpiece shown in FIG. 8.

To perform this, the following steps should be taken in order:

a. set the angle alpha (0:), or cone angle, of the workpiece drawing;

b. set the crown dimension Y" (usually between 0 and 0.0001 inches) tospecification;

c. set the angle theta (0), the rib face to track angle, (usuallyspecified at about 89 1?);

d. set the distance X" from rib cutter 35 to the centerline of trackcutter 34, in order to locate the crown at the center of the track;

e. set the height 2" of the rib face above the track;

f. The chamfer angle between rib face 55 and chamfer 56 is built intothe rib cutter itself, and is not adjustable. Alternatively a radiusmight be used. These settings as outlined above are accomplished asfollows:

a. The cone angle alpha (0:) (seen in FIG. 7 and FIG. 8), is the anglebetween the axis 72 of the workpiece and the face of the track cutter34. The correct angle is set by swiveling the wheel dresser baseplate 29about pivot 31 and locking the position by means of tee nuts 32 in slot33 (FIG. 4).

b. Setting the crown dimension Y to specification (FIG. 7 and 8) isaccomplished by tilting the face of the track cutter 34 slightly towardthe wheel from the vertical. The angle 1 is very small and is changed byswiveling the track-dressing cutter spindle 61 about the pivot 60 (seenin FIG. 3), and locking it using clamp screws 62. The method ofcalculating and Y" is described in our copending application Ser. No.594,460, filed Nov. 15, 1966 and issued as US. Pat. No. 3,481,3l9 onDec. 2, 1969.

c. The angle theta (0) (FlG. 7 and 8) is set by rotating the swivelplate 64 about its pivot 63 and locking it in position from below withclamp screws 65 (seen in FlG. 4).

d. The distance X (FIG. 7) is adjusted by sliding the gib plate 66 (FlG.3 and 4) with rib dressing cutter spindle 69 attached, along theguideway 67 milled in swivel plate 64. (A gib for this purpose ismachined on the bottom of gib plate 66). The adjustment is then clampedby screws 68 (seen in FlG. 2).

e. Dimension 2" is set by sliding rib dressing cutter spindle 69 along asquare key 70 set into the top of gib plate 66 and clampingit withscrews 71. This completes the setting of the cutters relative to eachother.

Before grinding, the position of the conjugate wheel dresser 28 must beset as a unit so that the grinding wheel 24 will be directly in front ofthe dresser at the dress position, and the workpiece will be directly infront of the grinding wheel at the grinding position. The method ofdoing this would be different for each type of form grinder on whichitis installed. ln this embodiment, workslide 14 is traversed as indicatedby arrow 15 between adjustable stops (not shown) at each end of travel.

On the typical form grinder illustrated in FIG. 1 the grinding wheel 24is shown in the grind position at work station 21, about to feed into aworkpiece 19a shown on the magnetic chuck 22. (An enlarged view of thisis shown in FIG. 8. Grinding wheel 24 is fed into the workpiece alongarrow 59 until the finished size stop (not shown) is reached, and thenbacked off along arrow 59in the reverse direction.

When the grinding wheel is clear of the work station, the workslide 14(which also carries the wheel dresser 28 seen in FIG. 1) is shiftedthrough the distance W" (shown in FIG. 7 and FIG. 8) as indicated byarrow 58. This brings the wheel dresser 28 carrying the dressing cutters34 and 35 into the position formerly occupied by workpiece 19a.

Prior to this movement W," the conjugate wheel dresser 28 must be raisedhydraulically to allow the dressing cutters 34 and 35 to clearthegrinding wheel during traverse.

When the translation movement W" is complete, the grinding wheel againcross feeds into the dress stop along arrow 57, and the conjugate wheeldresser 28 is lowered. First the rotating track-dressing cutter 34contacts the rotating grinding wheel 24, and passes by, removing a smallamount of the wheel to expose a new surface thereon.

Next the rib cutter 35 contacts and passes by the wheel, removing asmall portion and exposing a new surface thereon.

After both dressing cutters have passed the wheel 24, the elevator block36 reaches bottom, and remains there in preparation for the next dresscycle.

When the elevator block 36 is down, the work slide 14 is again movedback through the distance "W" (arrow 58) and a new workpiece is groundby infeed along arrow 59.

The dressing cycle is not necessarily called for each time a workpieceis ground. It varies with the size of the workpiece and the amount ofstock removal. Skip dress," as it is called, might be anywhere between Iand 20 workpieces of the type shown. 4

A description of the hydraulic circuit controlling the operation of theelevator will now be given with reference to PK]. 6. Essentially, itconsists of a solenoid operated, spring centered, four-way valve and athrottled flow control for speed adjustment in both up and down"directions. I

Prior to dressing, solenoid A 18 energized, shifting the valve to theleft and permitting the pressurized oil from pump P" to flow through thevalve and hydraulic line 43, check valve 44, variable restrictor 45, andline 46, to orifice 47 in baseplate 29. There is no flow throughrestrictor 49 because of check valve 48.

Through the internal passes in block 38, the pressurized oil is led tothe piston and rod assembly 40, causing it to rise at a rate controlledby the setting of variable restrictor 45.

When the solenoid is released, the valve returns to center as shown inthe diagram, trapping the oil in the cylinder and holding the elevatorup, where it will stay until released by solenoid B."

When it is desired to lower the conjugate wheel dresser 28, solenoid 8"is energized, which opens line 43 to sump 50 through the valve. Theweight of the elevator block 36 and the units mounted on it, force theoil out of cylinder 41 back through the orifice 47, line 46, check valve48, variable restrictor 49, and line 43. The rate of fall of theelevator block 36 is controlled by setting variable restrictor 49, sincecheck valve 44 prevents flow through restrictor 45.

It might be pointed out that the piston 40 is formed in two parts forreasons not essential to this invention.

An oil entrapment cushion to reduce the shock when the bottom isreached, is provided at the lower end of the cylinder in a manner wellknown to the art.

The rate of rise and fall are controlled by adjustment of the variablerestrictors 45 and 49, and need not be identical.

We have here disclosed only one embodiment of our mechanism, but itshould be understood that this design is not so limited, and otheruseful applications might be adopted well within the purview of theinvention.

We therefore claim:

1. A wheel-dressing apparatus for dressing a grinding wheel, saidgrinding wheel adapted to simultaneously grind a plurality of surfaceson a workpiece, said wheel-dressing apparatus comprising:

a. a baseplate;

b. an elevating block;

c. means for elevating said block;

d. a first dressing cutter mounted on a motor driven spindle on saidelevating block;

e. a second dressing cutter mounted on a second motor driven spindle onsaid elevating block;

f. said second dressing cutter mounted above and ofi'set substantiallynormal from said first dressing cutter;

Whereby said first dressing cutter contacts said grinding wheel on itsfront surface thereof, and said second dressing cutter contacts saidgrinding wheel on its back and edge surfaces as said block is elevatedpast said grinding wheel.

2. A wheel dressing apparatus as defined in claim 1, wherein said firstdressing cutter is defined as a track cutter and is tilted vertically,defined by the angle a, so as to provide a crowned surface on saidworkpiece by means of forming a minimal concave surface on said grindingwheel, defined by the dimension Y.

1. A wheel-dressing apparatus for dressing a grinding wheel, saidgrinding wheel adapted to simultaneously grind a plurality of surfaceson a workpiece, said wheel-dressing apparatus comprising: a. abaseplate; b. an elevating block; c. means for elevating said block; d.a first dressing cutter mounted on a motor driven spindle on saidelevating block; e. a second dressing cutter mounted on a second motordriven spindle on said elevating block; f. said second dressing cuttermounted above and offset substantially normal from said first dressingcutter; Whereby said first dressing cutter contacts said grinding wheelon its front surface thereof, and said second dressing cutter contactssaid grinding wheel on its back and edge surfaces as said block iselevated past said grinding wheel.
 2. A wheel dressing apparatus asdefined in claim 1, wherein said first dressing cutter is defined as atrack cutter and is tilted vertically, defined by the angle Alpha , soas to provide a crowned surface on said workpiece by means of forming aminimal concave surface on said grinding wheel, defined by the dimensionY.